Frequency stabilizing circuit



June 30, 1953 JACQBSEN 2,644,093

FREQUENCY STABILIZING CIRCUIT Filed Jan. 24, 1945 AAAAAAAA 111:

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AND/KW B. JACQSSEN BY m L fffiarm y Patented June 30, 1953 UNITED STATES PATENT OFFICE FREQUENCY STABILIZING CIRCUIT Andrew B. J acobsen, Cambridge, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary, of War Application January 24, 1945, Serial No. 574,373

4 Claims. 25036) This invention relates to electrical apparatus and more particularly to means for maintaining uniformity of operation of a multivibratorunder conditions of fluctuating power supply.

The precision delay multivibrator described herein is adapted for range measurement in radio-echo detection equipment. In such use the proper width of the pulses must be uniformly maintained to obtain accuracy in range measurement. To achieve this result it has been necessary heretofore to operate this type of multivibrator from a carefully regulated power supply.

It is an object of this invention to provide means for adjusting the grid bias of one of the multivibrator tubes to compensate for changes in plate and cathode-heater voltage so that operation will be uniform. Another object is to eliminate the necessity for the use of a regulated voltage supply.

The figure shows a diagram of a multivibrator circuit using the principles of this invention.

Referring now to the drawing, there are shown two triodes, I and 2, provided with plates t and I, grids and 8, and cathodes 6 and 9, respectively. Cathodes 6 and 9 are connected through a common cathode resistor H to ground. Plates 4 and l are connected through resistors I2 and [3, respectively, to a conductor M which leads from a source of positive potential at the power supply. Plate 4 of tube l is connected through a condenser :6 to the grid 8 of tube 2, which grid is connected through a large resistor l! to the aforesaid source of positive potential. 6 and 9 are supplied with heater current through wires is from the power supply.

One electrode 2| of a neon glow tube '2flis connected through a resistor 22 to the conductor M leading to the source of positive potential. Electrode 2i is also connected through a potentiometer 26'to ground. The other electrode 23 of glow tube 201s connected through a rheostat 24 to ground. The sliding contactor of potentiometer 26 is connected through a potentiometer 21 to ground. The sliding contactor ofpotentiometer 2'! is connected through a potentiometer 28 and a rheostat 30, connected in parallel, and then through a rheostat 32 and the wire 14 to the source of positive potential. The sliding contactor of potentiometer 28 is connected through a resistor 33 and the secondary 4| of a transformer to the grid of multivibrator tube 1. Condenser 43 is connected between ground and the junction of resistor 33 and secondary 4i. Potentiometer 2! and rheostat 32 are arranged for ganged operation.

In operation, the triode 2 is normally conduct- Cathodes ing, its grid Bbeing held at approximately the cathode potential by the grid'current through the large resistor IT. The current through the common cathode resistance II is suiiicient to make the cathode 6 of tube I positive with respect to the grid, and this tube is therefore nonconducting. In this condition, the current and voltage in the circuit are independent of the grid voltage of tube 2. The condenser I6 is charged to a voltage equal to the potential difference between .the plate 4 of tube l and the grid 8 of tube 2 because of the small grid current drawn by tube 2 through the resistor H.

A positive trigger pulse is applied to the primary 42 of transformer 4!! and through the secondary 4| to grid 5 of tube I. Tube l thereby becomes conducting, causing its plate voltage to drop. Through the medium of condenser [6, this drop in voltage affects the grid 8 of tube 2 so that the grid potential is driven below the new cathode potential. The cathode potential of tubes 1 and 2 falls immediately after occurrence of the trigger pulse to a value which is determined by thev bias applied to grid 5 of tube i. Under the conditions now prevailing in the the voltage at plate 4 which .in turn raises the i grid potential offtube 2 (through the condenser IE) thereby increasing the current in tube 2' and the multivibrator returnsijto the normal quiescent v conditionj The change o'ccurs very mess and ina'regenerating fashion. y

Any variation inthe alternating current supply will cause a corresponding variation in the voltage of the positive potential source and also a change in the cathode heater current. These changes, if not compensated for, produce a variation of pulse Widths corresponding to an error in range whenthe multivibrator is used as part of the apparatus for measuring range in radioecho equipment.

In the circuit herein described the voltage across the electrodes of neon glow tube 26 tends to remain constant and any increase or decrease in potential will be divided between resistor 22 and rheostat 24 in direct proportion to the resistance values of these elements. This causesv 3 the potential of electrode 21 to increase and decrease directly with increases and decreases of potential at the positive voltage source and by an amount depending on the ratio of the values of resistances 22 and 24.

The potential of electrode 2! is applied to potentiometer 26, and through its connections with the potentiometers and rheostats designated 21, 30, 28, and 32, controls'the bias of grid 5 so that the grid bias is changed an amount just sufiicient to compensate for changes in plate voltage and cathode heater voltage. The proper width of pulse is thus maintained throughoutdluctuations in applied voltage.

Potentiometer 21 and rheostats-30 and-32 com-' prise a calibrating network which-cooperates with range potentiometer 28 in range setting operaa tions. Range potentiometer 28 is varied in normal operation to vary the widths of the pulses produced by the multivibrator. Rheostat 30, which may be preset, determines the interval between the upper-and lower limitsof pulse-widths obtainable byadjustment of potentiometer 28. Potentiometer 21 and rheostat 32,-which-may also be preset, enable adjustment of'the minimum pulse widths obtainable by means of potentiometer 28 without materially-affecting the interval between the upper and lower limits of pulse widths.

What I claim to have invente'dis:

1. In combination, a'multivibrator circuit operated by fluctuating voltage source'and including an electronic discharge device having a control grid, said Voltage source including'upper and lower potentials, a glow tube connected in series between two resistors, said glow tube and said resistors :being connected between s'aid upper and lower potentials, said glow tube having at least two electrodes, a first potentiometerconnected between one electrode of said glow tube and the one of said potentials mostremote from said one electrode, said first potentiometer having an-ad-- justable center tap connected through a-second potentiometer to said one potential, said'second potentiometer having anadjustable center tap connected through a third potentiometerand a first rheostat connected in parallel and 'a -s'econd rheostat connected in series'to said other potential, said third potentiometer' havin anadju'stable center tap connected to said control-grid, and means coupled to saidcontrol meansto-cause said multivibrator to be triggered. I

2. In combination,- a multivibrator circuit operated by fluctuating voltage source and including an electronic discharge device having a control grid, said voltage source including-upper and lower potentials, a device havingtwo terminals across which the voltage tends to remain con-1 stant, said device being connected inseries be= tween two resistors, said device and said resistors being connected between said upper and lower potentials, a first potentiometer connected-between one electrode of said-device and the one of 4 said potentials most remote from said one electrode, said first potentiometer havin an adjustable center tap connected through a second potentiometer to said one potential, said second potentiometer having an adjustable center tap connected through a third potentiometer and a first rheostat connected in parallel and a second rheostat connected in series to' said other potential, said third potentiometer hav'irigan adjustable center tap connected to said control grid,

and means coupled to said control means to cause :said multivibrator to be triggered.

3. In combination with a multivibrator having an electronic discharge device including a control grid and supplied with a fluctuating voltage source, said multivibrator being arranged to producepulses of adjustable widths, first means including a glow tube to adjust the potential applied to saidcontrol grid to compensate for fluctuations of said voltage source, said first means including means for varying the widths of the pulses produced by said multivibrator, said first meansi'also including means for determining the interval between the upper and lower limits of said pulse widths, said first means also including means for adjusting the minimum pulse widths obtainable without materially afiecting the interval between upper and lower limits of'puls widths.

4. An oscillatory electrical circuitiincluding an electron discharge device having a controlgr id, a fluctuating voltage source, a potentiometer and a first rheostat connected in parallel, saidpa'rallel potentiometer and first rheostat being connected in series with and betweena sec'on'd rheostat and a third rheostat, the networkconsisting of said potentiometer and said first,-second and third rheostats being connected acrosssaid voltage source, said potentiometer including-an adjustable center tap connected to saidcontrol grid, and means coupled tosaid controlgrid to supply a triggering pulse to said'circu'it,

ANDREW 'BJJAC'OB'SENI Number 

